Leaflet:「Let’s Learn About: Pesticide Residues」
Understanding pesticides and their uses
According to the World Health Organization (WHO), there are more than 1,000 pesticides used around the world, each with different properties and toxicological effects. Pesticides are used to protect crops against insects, weeds, fungi, etc. so as to stabilise and increase crop yields. Some pesticides also regulate plant growth by stimulating or inhibiting the growth rate of plants, such as accelerating flowering and fruiting or delaying germination and ripening. In addition, many countries have banned the use of pesticides that have long-lasting impacts on soil and water sources to reduce their adverse effects on the environment and the hazards to human health caused by their residues in crops.
Relationship between pesticides and health
Some pesticides are potentially toxic to humans, and high doses can cause acute poisoning whose symptoms include vomiting, diarrhoea, abdominal pain, dizziness, and paralysis. In severe cases, the victim may have breathing difficulty, blurred vision, cramps or even death. Long-term exposure to low doses can result in chronic poisoning which may induce cancer, damage nerves, and disrupt the normal functioning of the reproductive and immune systems, leading to brain damage and abnormal development of embryos.
In view of the toxicity of pesticides and the varying degrees of hazards to human health, the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) conducted assessments and established the Acceptable Daily Intake (ADI) for different pesticides based on the assessments, while the Codex Committee on Pesticide Residues (CCPR) formulated a list of pesticides approved for use and their Maximum Residue Limits (MRLs) in food. These international standards are published on the website of Codex Alimentarius Commission so that different countries can apply the standards in monitoring the safety of domestic and imported food supplies and ensure that the amount of pesticides consumers are exposed to through food over their lifetime does not result in adverse health effects.
Regulation on use of pesticides in international arena
In today's international trade, pesticides which are genotoxic or carcinogenic are prohibited from use for growing food crops. The “Food Code” (Codex Alimentarius), which is a collection of internationally adopted food standards, has established the MRLs for over 100 commonly used pesticides. The food regulatory authorities collect food samples for chemical testing to prevent the levels of pesticide residues in imported and commercially available food from exceeding the safety limits. Moreover, the government of various countries control the use of pesticides through legislation and provision of education to farmers, which can protect crop yields and make sure that the doses are within the limits prescribed by international food safety standards. The use of biological pest control is also encouraged to minimise the use of pesticides as far as possible to safeguard public health.
Regulation of pesticide residues in food in Macao
The “Maximum Limits for Pesticide Residues in Food” of Macao came into effect in April 2020, setting out the maximum limits for 191 pesticide residues and the extraneous maximum residue limits for 5 pesticides in different types of food, totalling over 2,300 standards for limits of pesticide residues. They serve to ensure that the food safety standards in Macao can effectively regulate the safety of food, improve the protection of consumers’ health, and prevent the impact on stable food supplies.
Since the food in Macao are mainly imported, how can the food industry know about the levels of pesticide residues present in food?
In accordance with the import system of Macao, all live and fresh food imported to Macao is subject to mandatory inspection by IAM before releasing into the local market for sale to ensure residents’ consumption safety. The food industry should order food from reliable importers. In addition, they have the responsibility to find out whether the supplies comply with relevant requirements and obtain information about production from the importers, distributors or places of origin. As stipulated by the “Food Safety Law” of Macao, entities engaged in the production and operation of food have the obligation to keep records concerning delivery and reception of goods or relevant invoices to facilitate effective and timely food tracing and tracking when necessary.
The industry can make use of the “Guide on Food Classification of Maximum Limits for Pesticide Residues in Food” to look for the food classification, the scientific names, the maximum residue limits and other relevant technical information, to help them to operate in compliance with the related regulations.
How should residents reduce the risk of intake of pesticide residues in everyday life?
Since vegetables are the main source of dietary intake of pesticide residues of local residents, the established limits serve to specifically control the trace amounts of pesticide residues in them. As fruits and vegetables (e.g. green leafy vegetables, tomatoes and potatoes) are indispensable to a balanced diet, residents can further limit their intake of pesticide residues by peeling or washing them thoroughly with running water, which also reduces foodborne harmful bacteria.
Furthermore, the farms in Mainland China for supply to Macao are under supervision of national competent authorities, and the pesticides and doses used have to comply with national food safety standards. In general, the toxicity of pesticides weakens with time or for environmental factors, such as temperatures, amounts of rainfall, sunlight intensity and the effective period after application. By the time the crops are ready for harvest, the majority of pesticides in them have disappeared, only a trace level of residues in milligrams remain. Over the years, the results of pesticide residue testing of food by IAM showed no anomalies, so the public do not need to worry about pesticide residues in food.
All in all, we should maintain a balanced diet and eat various fruits and vegetables to avoid excessive intake of harmful substances due to picky-eating.